U.S. patent application number 11/731398 was filed with the patent office on 2008-10-02 for circuit arrangement with improved decoupling.
Invention is credited to Bernd Adler, Zdravko Boos.
Application Number | 20080242235 11/731398 |
Document ID | / |
Family ID | 39564783 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080242235 |
Kind Code |
A1 |
Adler; Bernd ; et
al. |
October 2, 2008 |
Circuit arrangement with improved decoupling
Abstract
A circuit arrangement includes a component having a closed
signal path, that closed signal path connected to a first port, a
second port and at least a third port. The component has a directed
signal flow of a signal applied to one of that ports. Such a
coupling device can be connected to a transmitter and to a receiver
path, respectively.
Inventors: |
Adler; Bernd; (Neubiberg,
DE) ; Boos; Zdravko; (Munchen, DE) |
Correspondence
Address: |
ESCHWEILER & ASSOCIATES LLC
629 EUCLID AVENUE, SUITE 1000, NATIONAL CITY BUILDING
CLEVELAND
OH
44114
US
|
Family ID: |
39564783 |
Appl. No.: |
11/731398 |
Filed: |
March 30, 2007 |
Current U.S.
Class: |
455/73 ; 455/338;
455/339; 455/340 |
Current CPC
Class: |
H04B 1/006 20130101;
H04B 1/406 20130101 |
Class at
Publication: |
455/73 ; 455/338;
455/339; 455/340 |
International
Class: |
H04B 1/16 20060101
H04B001/16 |
Claims
1. A circuit arrangement, comprising: a transmitter configured to
provide a transmission RF-signal; a receiver configured to receive
a reception RF-signal; an antenna signal path; and a coupling
device comprising a first port coupled to the transmitter, a second
port coupled to the antenna signal path, and a third port coupled
to the receiver, the coupling device comprising a signal
suppression component configured to suppress at least a signal from
the first port to the third port, and a signal from the second port
to the first port.
2. The circuit arrangement of claim 1, wherein the coupling device
comprises a circulator.
3. The circuit arrangement of claim 1, wherein the transmitter
comprises a first power amplifier configured to amplify a signal
having a first center frequency and at least a second power
amplifier configured to amplify a signal having a second center
frequency, wherein the first power amplifier and the at least one
second power amplifier are coupled to the first port.
4. The circuit arrangement of claim 3, further comprising a switch
configured to selectively couple one of the first and the at least
one second power amplifier to the first port.
5. The circuit arrangement of claim 3, wherein a first band-pass
filter is disposed between the first power amplifier and the first
port and a second band-pass filter is disposed between the at least
one second power amplifier and the first port.
6. The circuit arrangement of claim 1, wherein the receiver
comprises a first filter having a first pass-band and at least one
second filter having a second pass-band, wherein the first and
second filter are coupled to the third port.
7. The circuit arrangement of claim 1, further comprising a switch
disposed between the third port and the receiver, and configured to
pass a signal at the third port on one of at least two sub-paths of
the receiver in response to a control signal.
8. The circuit arrangement of claim 7, wherein the control signal
is derived from the center frequency of the signal at the third
port.
9. The circuit arrangement of claim 7, wherein the switch comprises
a duplexer switch having a common input terminal and at least two
output terminals.
10. The circuit arrangement of claim 1, wherein the coupling device
comprises a closed signal path, the signal path comprising a
directed signal flow with respect to a signal applied to one of the
first, second and third ports.
11. The circuit arrangement of claim 1, wherein the coupling device
comprises a circular conductor loop having the first, second and
third ports arranged with an angle of approximately 120.degree. to
each other.
12. The circuit arrangement of claim 1, wherein the antenna signal
path comprises an antenna and a directional coupler disposed
between the third port and the antenna.
13. The circuit arrangement of claim 1, further comprising at least
one matching network connected to at least one of the first, second
and third ports, and configured to match an impedance of a circuit
connected thereto to an impedance of a circuit connected to at
least one of the other ports.
14. A circuit arrangement, comprising: a transceiver configured to
provide a transmission signal on at least one first transmission
terminal, and receive a signal on at least one terminal of a
plurality of reception terminals; a circulator coupled to the at
least one first transmission terminal and to the plurality of
reception terminals; a matching network coupled to the circulator,
and configured to match an impedance of an antenna to an impedance
of the at least one first transmission terminal and the at least
one terminal of the plurality of reception terminals.
15. The circuit arrangement of claim 14, wherein the transceiver
comprises a first receiver path configured to receive a signal
having a first center frequency and at least one second receiver
path configured to receive a signal at a second center frequency,
wherein the first and at least one second receiver path are coupled
to the circulator.
16. The circuit arrangement of claim 15, wherein at least one of
the first and at least one second receiver path comprises a low
noise amplifier or a band-pass filter, or both.
17. The circuit arrangement of claim 14, further comprising: a
first band-pass filter disposed between the at least one terminal
of the plurality of reception terminals and the circulator; and at
least one second band-pass filter disposed between a second
terminal of the plurality of reception terminals and the
circulator.
18. The circuit arrangement of claim 14, wherein the transceiver
comprises a first transmitter path configured to provide a
transmission signal having a first center frequency and at least
one second transmitter path configured to provide a transmission
signal having a second center frequency, wherein the first and said
at least one second transmitter path are coupled to the
circulator.
19. The circuit arrangement of claim 18, wherein at least one of
the first and at least one second transmitter path comprises a
power amplifier or a band-pass filter, or both.
20. The circuit arrangement of claim 18, further comprising a first
band-pass filter disposed between the first transmitter path and
the circulator and at least one second band-pass filter disposed
between the at least one second transmission path and the
circulator.
21. The circuit arrangement of claim 18, further comprising a
switch having an output connected to the circulator and a plurality
of inputs, wherein each input is connected to one of the respective
first and at least one second transmitter path, and wherein the
switch is configured to connect the output to one input of the
plurality of inputs in response to a control signal.
22. The circuit arrangement of claim 21, wherein the control signal
is derived from a center frequency of the transmission signal.
23. The circuit arrangement of claim 14, further comprising a
switch having an input connected to the circulator and a plurality
of outputs, wherein each output is coupled to one respective
terminal of the plurality of reception terminals, and wherein the
switch is configured to connect the input to one output of the
plurality of outputs in response to a control signal.
24. The circuit arrangement of claim 23, wherein the control signal
is derived from a center frequency of the received signal.
25. The circuit arrangement of claim 14, wherein the matching
network comprises a directional coupler configured to measure a
signal portion of at least a reflected signal, wherein the
directional coupler is disposed between the circulator and the
antenna.
26. The circuit arrangement of claim 14, wherein an impedance of
the matching network is tunable in response to a tuning signal.
27. The circuit arrangement of claim 25, wherein an impedance of
the matching network is tunable in response to a tuning word,
wherein the tuning word derived by the reflected signal.
28. The circuit arrangement of claim 14, wherein the matching
network comprises a tunable element connected to a tuning
input.
29. The circuit arrangement of claim 28, wherein the tunable
element comprises at least a tunable capacitor or a tunable
inductor.
30. A circuit arrangement, comprising: a device comprising a closed
signal path, the closed signal path connected to a first port, to a
second port and to at least a third port, the closed signal path
comprising a directed signal flow with respect to a signal applied
to one of the first, second and third port; a tunable matching
network connected to the second port, the tunable matching network
configured to match an impedance of a circuit coupled thereto to an
impedance of at least a first circuits coupled to the third
port.
31. The circuit arrangement of claim 30, wherein the closed signal
path comprises a circular conductor loop.
32. The circuit arrangement of claim 30, wherein the device
comprises a magnetic material surrounding the closed signal
path.
33. The circuit arrangement of claim 30, wherein the first port,
the second port and the third port connected to the closed signal
path are arranged with an angle of approximately 120.degree. to
each other.
34. The circuit arrangement of claim 30, wherein the matching
network comprises a directional coupler configured to measure a
signal portion of at least a reflected signal, wherein the
directional coupler is disposed between the second port and the
circuit.
35. The circuit arrangement of claim 30, wherein an impedance of
the matching network is tunable in response to a tuning signal.
36. The circuit arrangement of claim 34, wherein an impedance of
the matching network is tunable in response to a tuning word,
wherein the tuning word is derived by the reflected signal.
37. The circuit arrangement of claim 30, wherein the matching
network comprises a tunable element connected to a tuning
input.
38. The circuit arrangement of claim 37, wherein the tunable
element comprises at least a tunable capacitor or a tunable
inductor.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a circuit arrangement, particularly
in the field of telecommunication.
BACKGROUND
[0002] Modern telecommunication standards often require a
simultaneous transmission and reception of signals. For example,
the third generation communication standard Wideband CDMA/UMTS
(Wideband Code Division Multiple Access, Universal Mobile
Telecommunication System) uses a frequency division duplex (FDD)
method to transmit continuous signals while receiving signals on a
different center frequency simultaneously. According to the
specification of the UMTS standard a total number of at least nine
different operating bands are specified. In each operating band, a
first frequency range is specified for transmitting signals by a
user device to be received by a base station. Concurrently, a
second frequency range is specified for the base station. The
transmitted signals are received by the user device. Because the
specification requires a good signal quality for an error-free
signal reception, it is necessary to suppress any interfering
signal coming from an external source or from simultaneous
transmitted signals sufficiently. It is also expected that more
frequency operating bands will be added into existing communication
standards or new standards with new operating bands will be
specified in the future.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The invention is explained in detail below using exemplary
embodiments with reference to the drawings in which
[0004] FIG. 1 shows a first embodiment of the invention,
[0005] FIG. 2 shows a second embodiment of the invention,
[0006] FIG. 3 shows a third embodiment of the invention,
[0007] FIG. 4 shows first embodiment of a circulator
arrangement,
[0008] FIG. 5 shows a second embodiment of a circulator
arrangement,
[0009] FIG. 6 shows a first embodiment of a tunable matching
network,
[0010] FIG. 7 shows a second embodiment of a tunable switching
network including a directional coupler,
[0011] FIG. 8 shows a third embodiment of a tunable matching
network,
[0012] FIG. 9 shows a fourth embodiment of a tunable matching
network,
[0013] FIG. 10 shows a first embodiment of a tunable capacitive
element for usage in a tunable matching network,
[0014] FIG. 11 shows a second embodiment of a tunable capacitive
element,
[0015] FIG. 12 shows a fourth embodiment the invention,
[0016] FIG. 13 shows a known transceiver arrangement.
DETAILED DESCRIPTION
[0017] In the following description, further aspects and
embodiments of the present invention are disclosed. In addition,
reference is made to the accompanying drawings which form a part
hereof, and in which is shown by way of illustration in which the
invention may be practiced. The embodiments of the drawings present
a discussion in order to provide a better understanding of one or
more aspects of the present invention. The disclosure is not
intended to limit the feature or key elements of the invention to a
specific embodiment. Rather, the different elements, aspects, and
features disclosed in the embodiments can be combined in different
ways by a person skilled in the art to achieve one or more
advantages of the present invention. It is to be understood that
other embodiments may be utilized and structural or logical changes
may be made without departing from the scope of the invention. The
elements of the drawings are not necessarily to scale relative to
each other. For illustration purposes, some frequency ranges and
communication standards are specified. The ranges as well as the
communication standards referred to are not restricted to the
embodiment disclosed herein. Other frequency and power ranges or
communication standards can also be used to achieve the different
aspects of the present invention. Like reference numerals may
designate corresponding similar parts.
[0018] In current transceiver arrangements, often a plurality of
signal paths for transmitted signals and received signals are used.
FIG. 13 shows a circuit arrangement comprising a transceiver 100.
The transceiver 100 is connected to a plurality of signal paths of
which only two are shown for illustration purposes. Each of the
signal paths comprises a power amplifier arrangement 200 and 300,
respectively. Each of the paths comprising the respective power
amplifiers is configured to amplify signals in a specific operating
band. While only two paths are shown, further paths, as indicated
by the dotted path, may be added, depending on the requirements of
the communication standard for which the transceiver is used.
[0019] The output of the amplifiers 200 and 300 are connected to
duplex filters 200a and 300a, respectively. These duplex filters
200a, 300a comprise a pass-band characteristic having steep edges
to sufficiently suppress interfering signals in adjacent channels.
The duplex filters may comprise in one embodiment at least two
band-pass filters with different filter characteristics and
pass-bands. One output of each duplex filter 200a, 300a is
connected to a terminal of a duplexer unit 600, coupling one of its
input terminals to a common output terminal in response to a
control signal. The output terminal is connected to an antenna for
receiving and transmitting signals. In operation, an amplified
signal is filtered and applied to one of the inputs of unit 600 for
transmission. Simultaneously the amplified signal is suppressed by
a second band-pass filter to prevent signal flow to a low noise
amplifier 500 connected thereto. A received signal in a different
frequency range is suppressed by the first band-pass filter of the
respective duplex filters 200a, 300a but passed by the second one
to the low noise amplifier 500. The low-noise amplifiers 500 are
connected to a plurality of band-pass filters 400 with a pass-band
characteristic enclosing the frequency range of the corresponding
operating band.
[0020] In the arrangement of FIG. 13, the transfer requirements of
the switch with respect to, for example, linearity are very tough
because a high-power transmission signal is passing through the
switch while at the same time a low-power signal and a number of
external interferers are received, filtered and applied to the
corresponding low-noise amplifier 500. Consequently, the duplex
filters 200a and 300a require steep flanks or edges and sufficient
suppression in adjacent channels not only for the band-pass filter
of the receiver path but also for the band-pass filter in the
transmitter path because interference signals may change the
reflection behavior of the antenna causing reflection at the output
of the power amplifiers 200 and 300.
[0021] The proposed circuit arrangement comprises a transmitter
path to provide an RF-signal, a receiver path to receive an
RF-signal, and an antenna signal path. A coupling device coupled
with a first port to the transmitter path, with a second port to
the antenna signal path and with a third port to the receiver path
comprises signal suppression characteristic for a signal flowing
from the first port to the third port and for a signal from the
second port to the first port.
[0022] The proposal relaxes the requirements for elements in the
transmitter and receiver path with respect to linearity and
adjacent channel suppression because a signal to be transmitted
does not pass to the receiver side. Further, any signal received at
the second port is suppressed when applied to the first port. Due
to the directed signal flow of the coupling device, a signal
provided at one port is suppressed when flowing into the opposite
direction. Consequently, a signal applied to the first port is
directed to the second port while being suppressed at the third
port. A signal applied at the second port is suppressed with
respect to a first port but let passed to the third port.
[0023] In a further embodiment, the coupling device may comprise a
circular signal path, the signal path comprising a directed signal
flow of a signal applied to one of the first, second and third
port. In accordance with another embodiment, the coupling device
comprises a circular conductor loop having the first, second, and
third port arranged with an angle of approximately 120.degree. to
each other. The conductor loop may also be annular. In an
embodiment, the coupling device comprises a circulator.
[0024] In accordance with another embodiment, the transmitter path
may comprise a first power amplifier to amplify a signal having a
first center frequency and at least a second power amplifier to
amplify a signal having a second center frequency. The power
amplifiers may be coupled to the first port of the coupling device.
In one embodiment, a switch may be disposed between the first and
at least one second power amplifier and the first port of the
coupling device. In another embodiment, band-pass filters may be
disposed between the respective power amplifiers and the first port
of the coupling device. With the additional band-pass filters
arranged on the output of the power amplifiers, harmonic portions
caused by the amplification process may be suppressed and adjacent
channel leakage power reduced.
[0025] Another embodiment of the invention relates to a reduction
of interference signals in the receiver path. In this embodiment, a
first and at least a second filter may be arranged between a third
port of the coupling device and the receiver path. The first and at
least one second filter may comprise a band-pass filter having a
pass-band within different frequency regions. These frequency
regions may be overlapping or non-overlapping. In accordance with
another embodiment, a switch or a duplexer may be disposed between
the third port of the coupling device and the receiver path to
apply a signal provided by the third port of the coupling device to
one of at least two sub-paths of the receiver path in response to a
control signal. Consequently, a sub-path of the receiver path can
be selected in response to the control signal connecting the
respective sub-path to the third port for processing a received
signal provided at the third port of the coupling device. Each of
the sub-paths of the receiver path may comprise a filter and/or a
low noise amplifier. The filter may have different pass-bands. In a
further embodiment, the control signal may be derived from a center
frequency of the signal provided at the third port.
[0026] In yet another embodiment of the invention, the antenna
signal path may comprise an antenna and a directional coupler
disposed between the second port and the antenna. With a
directional coupler, reflection and transmission coefficients of
the third port can be determined and the results used for
controlling the transmitter or receiver path of the circuit
arrangement. In a further embodiment, the antenna signal path may
also comprise a matching circuit to match the impedance of an
antenna to an impedance on the first and third port of the coupling
device. The matching network may be tunable by a control word,
which, for example, can be provided by a signal derived from the
results of the directional coupler. With a matching network coupled
at least to the second port of the coupling device, the
transmission and suppression characteristics may be improved.
[0027] In yet another embodiment, a circuit arrangement may
comprise a transceiver to provide a transmission signal on at least
a first transmission terminal and to receive a signal on at least
one terminal of a plurality of reception terminals. A circulator is
coupled to the at least one first transmission terminal and to the
plurality of reception terminals. A matching network may be coupled
to the circulator to match an impedance of an antenna to an
impedance of the at least one first transmission terminal and the
at least one terminal of the plurality of reception terminals
coupled to the circulator. The matching network coupled to the
circulator reduces any antenna mismatch and, consequently, prevents
signal components of the transmission signals to be applied to one
of the reception terminals.
[0028] In a further embodiment, band-pass filters may be disposed
between the reception terminals and the circulator. Each of the
band-pass filters may comprise a different pass-band. In another
embodiment, the transceiver may comprise a first transmitter path
to provide a transmission signal having a first center frequency
and at least one second transmitter path to provide a transmission
signal having a second center frequency. Both transmitter paths may
be coupled to the circulator.
[0029] In one embodiment, both transmitter paths are coupled to the
circulator by a first band-pass and a respective second band-pass
filter. Such filters may be disposed between an output of the
transmission paths and a first port of the circulator. In another
embodiment, the circuit arrangement may comprise a switch having an
output connected to the first port of the circulator and a
plurality of inputs, each input connected to one of the respective
first and at least one second transmitter paths. The switch is
configured to connect the output to one input of the plurality of
inputs in response to a control signal. In yet another embodiment,
a switch may also be arranged between the circulator and the
plurality of reception terminals. The switch may connect the third
port of the circulator to one terminal of the plurality of the
reception terminals in response to a control signal. Both control
signals for the switches can be derived from a center frequency of
the received signal, for example.
[0030] In yet another embodiment, a circuit arrangement comprises a
circuit, the circuit having a closed signal path, the closed signal
path connected to a first port, a second port and at least a third
port. The closed signal path comprises a directed signal flow of a
signal applied to one of said first, second and third ports. A
tunable matching network is connected to the second port to match
an impedance of a device coupled thereto to an impedance of at
least a first device coupled to the third port. In one embodiment,
the circuit may comprise a circular or ring-shaped conductor loop
having the first, second, and third port arranged with an angle of
approximately 120.degree. to each other. In such circuit
arrangement, the circuit with the conductor loop comprises a
transmitting path between the first and the second port and the
second and third port while having a broadband suppression between
the first and third port as well as between the second port and the
first port. In one embodiment, the component comprises a circulator
having, for example, a Faraday rotator. In yet another embodiment,
the circular conductor loop may be surrounded by a ferrite material
resulting in different propagation velocities, thereby canceling of
waves propagating over two different paths. The component may be
based on a strip line cable or a micro strip.
[0031] FIG. 1 shows a first embodiment illustrating various
features of the invention. The circuit arrangement according to
FIG. 1 comprises a transmitter path 1c including a power amplifier
chain 2. The transmitter path 1c may comprise in one embodiment
circuits and devices for signal base band processing as well as for
frequency conversion to provide an RF-signal within the desired
frequency range. For example, the transmitter path 1c may comprise
an IQ-modulator, an OFDM-modulator, a polar transmitter, a polar
modulator and the like. Base band signal processing as well as
frequency conversion can be implemented in an integrated circuit
having an output connected to the amplifier chain 2.
[0032] The amplifier chain 2 comprises one or a plurality of
amplifiers connected in series. Often, the power amplifier chain 2
is a separate arrangement due to the generation of high signal
power, which may interfere with other devices or circuits of the
transmitter path. However, it is also possible in one embodiment to
implement some or all amplifiers of the power amplifier chain 2
within an integrated circuit also comprising other signal
processing circuitry. Some or all of the amplifiers of the power
amplifier chain 2 may comprise a tunable amplification gain, which
can be controlled by a microprocessor of the transmitter path. The
output of the last power amplifier of the power amplifier chain 2
of the transmitter path 1c is coupled to a first input terminal 41
of a circulator 4.
[0033] The circulator 4 is implemented in one embodiment as a three
port "turnstile" or Y-junction circulator based on cancellation of
waves propagating over two different paths near a magnetized
material. The output of the power amplifier chain 2 is connected to
a first port P1 of the circulator 4 at input terminal 41. A second
port P2 of the circulator 4 at terminal 43 is coupled to an antenna
7 for transmitting signals generated by the transmitter path 1c.
The circulator 4 further comprises a third port P3 at terminal 44
that is connected to a first duplexer switch 6. The input of the
duplexer switch 6 is connected to one of a plurality of output
terminals of switch 6 in response to a control signal.
[0034] Each of the output terminals of the duplexer switch 6 is
connected to a filter 8 having a pass-band transfer characteristic
within a specific frequency region. In one embodiment, these
regions are selected according to the specification of a mobile
communication standard. For example, the band-pass characteristic
of the filters 8 are in accordance to the frequency regions defined
in the different operating bands of the WCDMA mobile communication
standard. The band-pass filters 8 further transform an unbalanced,
also called single-ended signal provided by the circulator 4 and
the switch 6 to a balanced or double-ended differential signal
applied to a receiver path 1b. The receiver path 1b may comprise
low-noise amplifiers and frequency conversion circuitry to convert
a signal provided by one of the filters 8 to a down-converted
signal for further signal processing like, for example, base band
filtering, analog-to-digital conversion and demodulation.
[0035] The circulator 4 as used in the embodiment of FIG. 1 may be
a passive electronic component with three or more ports. The ports
can be accessed in such an order that when a signal is fed into any
port, it is transferred to the next port, the first being counted
as following the last in numeric order. Due to the cancellation of
waves propagating over two different signal paths near a magnetized
material, a circulator provides a directed signal flow resulting in
transmitting a signal from one port to the following port but
providing a broadband isolation for signals flowing in the opposite
direction. There are various ways of implementing a three port
Y-junction circulator and all alternatives are contemplated as
falling within the scope of the invention. In a three port ferrite
circulator, there are three transmission lines spaced radially
about a general cylindrical ferrite element subject to an
appropriate magnetic field. Electromagnetic energy transmitted
toward the ferrite element along a first transmission line is
transmitted out along the next adjacent line, spaced approximately
120.degree. apart. If there are more transmission lines, they are
connected to a center area with generally equal angles in degrees
apart. The transmission line may be microstrip lines, waveguides or
metallic strip spaced from a ground plane by a dielectric
layer.
[0036] In the circulator 4, a signal at the first port P1 and
terminal 41 circulates to the second port P2 while being suppressed
at the third port P3. A signal at the second port P2 is passed to
the third port P3 and terminal 45 but is suppressed in the
direction of the first port P1. As a result, a circulator 4
suppresses any amplified signal by the transmitter path 1c from
being provided at the third port. The characteristics to suppress
transmitted signal and transmitter noise in the receiver direction
at terminal 44 and interferers coming from the antenna 7 in the
transmitter output direction at terminal 41 relax the requirements
of the switch 6 and the duplexers 8 connected downstream. In
addition, reflection in the transmitter path due to mismatch at the
output of the amplifier may be reduced.
[0037] When a signal is received via the antenna 7 according to the
WCDMA mobile communication standard for example, the center
frequency of the received signal may be known to the microprocessor
within the receiver path 1b. The microprocessor provides a control
signal to the duplexer switch 6 connecting the third port P3 of
circulator 4 at terminal 44 to one of the filters 8 having a
pass-band transfer characteristic corresponding to the center
frequency of the received signal. Interferers outside the frequency
region of within the received signal as well as the signal
components provided simultaneously by the transmitter path 1c are
suppressed by the circulator 4 and the filters 8.
[0038] FIG. 2 shows a further embodiment of a circuit arrangement,
in which the receiver path and the portions of the transmitter path
are implemented in an integrated circuit 1a. The integrated circuit
1a shown herein comprises circuits for analog signal processing.
Data processing like demodulation or modulation is implemented in a
base band circuit arrangement connected to circuit 1a in one
embodiment. The integrated circuit 1a comprises a transmitter path
having differential inputs 152 to 155 for balanced analog I/Q
signals. Such I/Q signals represent the data to be transmitted and
are up-converted by an I/Q modulator to the desired frequency
range. For this purpose, the I/Q-modulator comprises a first mixer
133 and a second mixer 134. The first mixer 133 is connected with
its first input to a base band filter 140, which suppresses
harmonic and non-harmonic spurious signal components in the
I-component of the signal to be transmitted. In accordance, the
second mixer 134 of the I/Q modulator is coupled to a base band
filter 140, the filter 140 connected to terminals 154, 155 for
receiving the Q-component as well.
[0039] Local input terminals of mixers 133 and 134 are connected to
a frequency divider 17 coupled to a voltage controlled oscillator
19 providing an LO-signal. With the LO-signal at the local input
terminals, the mixers 133, 134 convert the low frequency I- and
Q-components to an RF signal at the desired frequency range. The
divider 17 provides the required phase shift of 90.degree. for the
I/Q-modulation. The output of the mixers 133, 134 are connected to
a circuit 121 adding both up-converted components and providing an
RF-signal to a balanced pre-amplifier 12. The pre-amplifier 12
comprises an adjustable gain controlled by a microprocessor unit
11.
[0040] Depending on the center frequency of the signal to be
transmitted, different power amplifier or power amplifier chains
can be used. For this purpose, the output of the balanced
pre-amplifier 12 is connected to a first power amplifier
arrangement 2 and a second power amplifier arrangement 3. The
amplifier arrangements 2, 3 also convert the balanced input signals
to an unbalanced amplified output signal. Further, both power
amplifier arrangements 2, 3 may comprise one or a plurality of
power amplifiers connected in series, some or all of them having
adjustable gain amplification. Accordingly, each of the power
amplifier arrangements 2 and 3 comprise a control input 21, 31 for
control words. The control inputs 21, 31 are connected to the
microprocessor unit 11 of the integrated circuit 1a. The
microprocessor unit 11 controls the amplification gain and the
total output power. Depending on the center frequency of the signal
to be transmitted, the power amplifier arrangement not required for
amplification can be switched off by, for example, a proper biasing
or separating the input of the arrangement not required from the
pre-amplifier 12. A corresponding control word is provided by the
microprocessor unit 11.
[0041] The unbalanced outputs of the power amplifier arrangements 2
and 3 are connected to respective input terminals 41, 42 of a
circulator arrangement 4. The circulator arrangement 4 comprises a
circulator 4a as well as a first switch coupling one of the input
terminals 41 and 42, respectively, to the first port of the
circulator 4a in response to a control word at terminal 45. The
control word at terminal 45 is provided by the microprocessor 11 in
one embodiment. The switch within the circulator arrangement 4 may
be implemented as transmission gates, transistors, diodes or other
switching elements. The circulator 4a of the circulator arrangement
4 comprises a second port connected to an antenna 7 by terminal 43
and a third port coupled to the output terminal 44 of the
arrangement 4. The terminal 44 is connected to a further switching
device 60 within the integrated circuit 1a.
[0042] In this embodiment, the switching device 60 comprises two
outputs connected to a first band-pass filter 80 and a second
band-pass filter 81, respectively. The output of the band-pass
filters are coupled to low-noise amplifiers 90, 91 providing a
low-noise amplification for the filtered signals and convert the
unbalanced signals into balanced signals. The outputs of the
low-noise amplifiers are connected to a further amplifier 10 with
an adjustable gain. The amplifier 10 is used to adjust the
amplitude of the received and amplified signal for the frequency
down-conversion in the I/Q demodulator connected downstream.
[0043] For this purpose, the output of the amplifier 10 is
connected to a first mixer 130 and a second mixer 131 of an
I/Q-demodulator, each comprising local oscillator input terminals
connected to a frequency divider 17. Its input is connected to a
voltage controlled oscillator 18. The outputs of both mixers 130,
131 of the I/Q demodulator are connected to respective low-pass
filters 141 for suppressing harmonics or sub-harmonics spurious
generated during down conversion. The down-converted and
demodulated components I and Q are provided at respective
analog-digital converters 142. The outputs of the analog-digital
converters 142 are connected to terminals 150 and 151.
[0044] During operation, the signals may be transmitted and
received on different center frequencies simultaneously. Such
operation mode is called frequency division duplex or FDD. The
center frequencies according to an operating band as set forth in
the mobile communication standard WCDMA are adjusted by the
microprocessor 11 by setting the phase-locked loops 180 and 190 to
proper values. The phase-locked loops are connected to voltage
controlled oscillators 18 and 19 for providing balanced signals at
double frequencies. These signals are applied to the dividers 17 in
the I/Q-modulator and I/Q-demodulator, which divide the frequencies
by the factor of two and provide a phase shift of 90.degree. as
indicated in FIG. 2.
[0045] While in this embodiment only two amplifier paths and
receiver paths are shown for illustration, a plurality of amplifier
and receiver paths are possible. For example, the WCDMA mobile
communication standard in FDD mode specifies at least nine
operating bands. Each operating band comprises a first frequency
region for signals to be transmitted and a second different
frequency region for receiving signals. In each frequency region of
each operating band, one or several transmission or reception
channels of 5 MHz bandwidth are specified. While some operating
bands may comprise overlapping frequency regions, the frequency
regions for transmission and reception in each operating band may
be different. Other frequency regions may be used for different
mobile communication standards.
[0046] As a result, the circuit arrangement may comprise a
plurality of transmitter paths, each having at least some filters
and/or power amplifiers. The circuit arrangement may also comprise
a plurality of receiver paths each of them comprising filters and
low-noise amplifiers connected thereto. Moreover, it is also
possible to connect a first broadband low-noise amplifier between
the output terminal of the circulator arrangement 4 and the input
terminal of switch 60 in circuit 1a.
[0047] FIG. 4 shows one embodiment of a circulator arrangement 4
having a circulator 40a and switch 48 connected to the first port
P1 of the circulator 40a. The switch 48 is implemented using
transmission gates and controlled in response to a signal at
control input terminal 45. The terminal 41, 42 can be connected to
different circuits and devices, for example to different amplifiers
or different transmission paths of a transmitter or transceiver.
While in this illustration the switch 48 comprises only two input
terminals 41, 42, a plurality of input terminals depending on the
number of amplifier paths is possible.
[0048] FIG. 5 shows an alternative embodiment using band-pass
filters 46 and 47 connected between the output of respective
devices, like amplifiers of a transmitter path and the first port
of the circulator 40a. The band-pass filters 46 and 47,
respectively, provide a sufficient suppression for harmonic and
other spurious signals and further relax the matching requirements
between the first port P1 of the circulator 40a and the output
terminal of the devices connected to terminals 41, 42. Further,
while only two filters 46 and 47 are shown herein, a plurality of
additional filters connected to the first port and to the
respective power amplifiers are possible. As an alternative
embodiment, matching networks can be disposed between the first
port P1 of the circulator 40a and the respective terminals 41, 42.
As an example, the matching networks may replace the filters 46 and
47, but can also disposed together with the filters between the
port P1 and the terminals 41, 42. The matching network match the
impedance of devices connected to terminals 41, 42 to an impedance
of the circulator 40a or devices connected to the other port of
circulator 40a.
[0049] The circulator arrangement according to FIG. 4 and FIG. 5
including the switches 48 or the band-pass filters 46 and 47 can be
implemented as a single device, but also with discrete elements.
Further, in another embodiment the switch 48 and the filters 46 and
47 can be separated from the circulator 40a.
[0050] With the use of a circulator, the antenna connected thereto
can be used for simultaneous transmission and reception of signals.
However, to provide a proper suppression by the circulator, the
impedances on two respective ports of the circulator should match
with each other. While the requirement of matching impedance can be
achieved for the transmitter path and the receiver path with proper
design, the impedance of an antenna connected to the second port of
the circulator may vary due to external parameters.
[0051] FIG. 12 shows an embodiment including devices for proper
matching. The circulator 40a comprises a first port, which can be
connected to a plurality of input elements, and a third port
connected, for example, to a switching element 6. The impedances at
the third port and the first port are matched. Matching between the
elements at the third and first port can be achieved by proper
design of the circuits connected thereto or additional matching
networks arranged between the circuits and the first and third
port, respectively. The second port P2 of the circulator is coupled
in one embodiment to a tunable matching network 5, which is
disposed between an antenna 7 and the second port of the circulator
40a. The tunable matching network 5 comprises a control terminal 55
for a respective control signal. If the impedance of the antenna 7
varies over time, the tunable matching network 5 will able to
compensate the impedance change of antenna 7. With this
arrangement, a matching impedance on each of the first, second, and
third port of the circulator 40a is achieved resulting in a good
transmission characteristic for signals from the first port P1 to
the second port P2 as well as from the second port P2 to the third
port P3 while at the same time providing a broadband suppression
for signals flowing from the third port P3 to the first port P1 and
from the second port P2 to the first port P1.
[0052] FIG. 3 shows an embodiment of a transmitter arrangement
including a matching network 5 between the second port P2 of a
circulator arrangement 4 at terminal 43 and the antenna 7. The
matching network 5 shown in FIG. 3 comprises a directional coupler
for decoupling a signal portion A in the forward direction as well
as a portion B of the reflected signal. The signal portions A, B
are used to calculate a reflection coefficient, said coefficient
representing information about a mismatch of an impedance between
ports P2 and port P1, P3 of the circulator arrangement 4. The
matching network 5 also comprises a tuning input 55, which is
connected to a control circuit within the transceiver device 1. A
control word at terminal 55 may be applied in response to the
measured reflection coefficients.
[0053] The transceiver device 1 comprises a plurality of output
terminals for signals to be transmitted connected downstream to a
power amplifier arrangement 2. The power amplifier arrangement 2
may comprise plurality of amplifier and a switch, its output
coupled to the first port of the circulator via terminal 41. A
third port P1 of the circulator within the circulator arrangement 4
is coupled to a switching device 6, connected downstream to a
plurality of filters 8. During operation, a signal is amplified by
the power amplifier arrangement 2 and transmitted by the antenna 7
while a signal received by the antenna 7 is applied to one of the
filters 8. Transmitted and reflected power is measured by the
directional coupler within the tunable matching network 5. If the
reflection coefficient changes by external parameters influencing
the impedance of antenna 7, a tuning control word is generated in
response to the measured reflection coefficient change. The
impedance mismatch of antenna 7 is corrected by the matching
network 5 to the corresponding impedance at ports P1 and P3 of the
circulator device 4.
[0054] FIG. 6 shows an embodiment of a tunable matching network 5
including a directional coupler for measuring a signal portion A in
forward direction as well as a second signal portion B of the
reflected signal in the opposite direction. In this embodiment, the
tuning input 55 provides a common control word to different tuning
elements of the matching network 5.
[0055] In the embodiment according to FIG. 7, a first and a second
tuning input 55 is provided, each of the inputs connected to a
separate tuning element of the matching network 5. Consequently,
the matching network 5 may comprise a plurality of different tuning
elements, which can be tuned separately or by a common tuning
word.
[0056] FIG. 8 shows a further embodiment of a tunable matching
network 5. The matching network 5 comprises two elements 500 and
501 connected in series between the input terminal 53 and the
output terminal 55. Both elements 500, 501 comprise an inductance.
Between the elements 500 and 501, a first node 508 is connected to
a first tunable capacitor 506. A second terminal of the capacitor
506 is connected to ground terminal 505. A second node 508 between
the second element 501 and the output terminal 54 is also connected
to a tunable capacitor 506. Control terminals of the tunable
capacitors 506 are connected to the tuning input 55 for a
corresponding control word. The capacitors 506 can also be used in
the embodiments according to FIGS. 6 and 7 as tuning elements.
[0057] Another embodiment with a tunable inductive element is seen
in FIG. 9. The tunable inductive element 502 is connected between
the input terminal 53 and the output terminal 54 of the matching
network 5. Further, a fixed capacitor 507 is arranged between the
output terminal 54 and the ground terminal 505. By changing the
capacitance of the tunable capacitors according to FIG. 8 or the
inductance of the tunable inductive element 502, the impedance of
the matching network changes. Accordingly, the impedances of
elements connected to terminals 53 and 54, respectively can be
matched to each other. The tunable inductive device can be
implemented in the matching networks according to FIGS. 6 and 7 as
well.
[0058] FIG. 10 shows an embodiment of a tunable capacitor 506,
which can be implemented in the embodiment of FIG. 8 for example.
The tunable capacitive element 506 comprises a first capacitor 511
and a second capacitor 512, connected in series between node 508
and ground terminal 505. A node between the capacitors 511 and 512
is coupled to a series circuit of a capacitor 510 and a switching
transistor 520. The gate of the switching transistor 520 is coupled
to the tuning input terminal 55 for the control bit STC. In
response to the control bit STC, the capacitor 510 is switched
parallel to the capacitor 512 resulting in an overall capacitance
change of the element 506.
[0059] FIG. 11 shows a further embodiment of a tunable capacitive
element 506. In this embodiment, a plurality of pairs of capacitors
530a, 531a to 530e, 531e are arranged in parallel between the
ground terminal 505 and node terminal 508. Between each pair of
capacitors 530a, 531a to 530e, 531e, a node is connected to a first
terminal of a respective switching transistor 532a to 532e. The
second terminal of each switching transistor 532a to 532e is
connected to a common ground terminal 505. The gates of the
switching transistors 532a to 532e are connected to the tuning
input terminal 55. With a proper control word STC' at the tuning
input terminal 55, the capacitors 531a to 531e can be selectively
switched on or off, thereby changing the overall capacitance of the
element 506.
[0060] The tunable capacitive elements 506 shown in the embodiments
according to FIG. 10 and FIG. 11 can also be implemented using
varactor diodes. For example, the capacitors 530a to 530e and 531a
to 531e in the embodiment according to FIG. 11 can be replaced by
varactor diodes. Of course, other matching network circuitry also
comprising resistive elements can be used. The embodiments of FIGS.
10 and 11 can be implemented in the matching networks according to
the embodiments in FIGS. 6 to 8.
[0061] With the invention, a circulator is used to reduce the
complexity of a duplex filter array in a multi-band communication
system. The circulator already suppresses interfering signals
coming from a transmitter in the receiver direction due to its
directed signal flow characteristic. Additional interfering signals
from the antenna applied to the receiver path can be sufficiently
suppressed by corresponding band-pass filters in the receiver path.
In addition, these filters may also further suppress any spurious
signal induced by the transmitter. Because of the high transmitter
path signal suppression due to the circulator and additional
band-pass filters that can be arranged in the receiver path, the
requirements for a low-noise amplifier or switches in the receiver
path in respect to linearity may be reduced. The arrangement
enables to use low power and coil less low-noise amplifiers. The
terminals mentioned herein may be adopted to receive or provide
unbalanced or balanced signals.
[0062] The low insertion loss of the circulator in addition to a
possible antenna tuning network enables the transmitter signal path
not only for third generation communication standards like WCDMA
but also for second and 2.5 generation like GSM, EDGE or PCS as
well as fourth generation (4G) mobile communication standards. In
the case that power amplifiers with non-linear transfer
characteristics are used, polar transmitters or S-class amplifiers
are possible in the transmitter path.
[0063] The different features of the embodiments shown herein can
be combined by one skilled in the art to achieve one or more
advantages of the present invention. Although specific embodiments
have been illustrated and described, it will be appreciated by one
of ordinary skill in the art that any arrangement that is
calculated to achieve the same purpose may be substituted for the
specific embodiment shown. It is to be understood that the above
description is intended to be illustrative and not restrictive. The
application is intended to cover any variations of the invention.
The scope of the invention includes any other embodiments and
applications in which the above structures and methods may be used.
The scope of the invention should therefore be determined with
reference to the appended claims along with the scope of
equivalence to which such claims are entitled.
[0064] It is emphasized that the abstract is provided to comply
with 37 CFR. Section 1.72(b) requiring an abstract that will allow
the reader to quickly ascertain the nature and gist of a technical
disclosure. It is submitted with the understanding that it will not
be used to interpret or limit the scope of meaning of the
claims.
* * * * *